Light-emitting diodes (LEDs) are widely used in various lamps due to the advantages of long lifetime, low power consumption, high luminance, and good environmental protection, etc., and have replaced the conventional light source such as the filament lamp.
Referring to FIG. 1, a typical LED lamp 10 comprises a base 11, at least one LED 12 arranged on the base 11, and an optical protective cover 13 covering the base 11 and the LED 12. The LED 12 is used as the light source to emit light. However, since the LED 12 generally emits the light forwards within a certain angle, the typical LED lamp 10 only emits the light forwards within the certain angle. That is, the typical LED lamp 10 only provides the light within a angle range of 0˜90 degrees rather than provides the light within a angle range of 0˜180 degrees, wherein the light comes upward and is parallel to a reference surface 14 that is vertical to the base 11, and the angle between the light and the reference surface 14 is 0 degree; and the light comes downward and is parallel to the reference surface 14, the angle between the light and the reference surface 14 is 180 degrees.
However, according to the program requirement for integral LED lamps published by Energy Star, at least 5% of total lumens must be emitted in the 13˜180 degrees zone. That is, the lamp needs to emit the light backward, but the typical LED lamp 10 cannot satisfy such requirement.